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Hi. I need some advice on the timing chain rattle I have picked up on my 320i.
I was advised to change the chain tensioner, which I did, the rattle went away for about 2 weeks and came back. Now they tell me I must have the cams/chain/guides changed as well. I cannot afford to do all that now. Do I genuinely have to change the cams, can I get away with just changing the guides and chain.

I had to replace the chain guides in my Altima SEr recently. What had happened was the chain guides broke and slid down allowing the tensioner to push all the way in but not on the guide and the rattle would only go away when there was enough oil flowing. I did not change any cams but just did the waterpump (which was sealed and on the inside), guides, tensioner, and seals. Runs like a champ but I did it myself and it was pretty darn hairy and scary to do a FWD V-6 with no room. I have no idea how the BMW would be to do but if you do a parts search for the chain guides and find they're plastic with a hook on the top side, it's a good bet something similar happened. You just don't know until you get in there and see if any damage was done. But as long as the chain is still circulating and hasn't broke, you're probably OK!

Edit:
Also, just found this...may just need an "upgraded tensionser". I'd try that first:

...Spent some more time researching and Pelican Parts has some detailed instructions and pictures for this engine/issue. Do a search for BMW 320i Tensioner Repair Pelican Parts, or Project 13 Pelican Parts. Should get you there one way or another.